1. Field of the Invention
The present invention relates to an in-vehicle battery charging system used to charge an object to be charged that includes an energy receiving unit and a rechargeable battery.
2. Description of the Related Art
Heretofore, as this sort of contactless charging system, there has been disclosed a battery charging system comprising: a battery charger with a built-in primary coil; and an object to be charged including a secondary coil and a rechargeable battery, in which the battery charger and the object to be charged are allowed to come close to each other to charge the rechargeable battery through an electromagnetic inductive action between both the coils. This battery charging system includes a holding unit for performing at least two-stage adjustment of a battery charging distance between the battery charger and the object to be charged, and thus due to its ability to adjust a charging current to a specific value and then to feed the same, only one battery charger of this type suffices to charge even a plurality of objects to be charged that are different in charging current, as disclosed in, e.g., Japanese unexamined patent application publication No. 2000-139033.
According to the foregoing battery charging system, however, in order to let a stick-like holder hold the object to be charged, the object needs to be provided with a portion to engage with the holder. Further, the publication No. 2000-139033 also discloses that a support portion is provided on a battery charger placing surface in a manner extending obliquely upwards, while this placing surface is partly formed with a tilted surface arranged orthogonal to an inclined face of the support portion, whereby when the object to be charged is placed on the tilted surface so as to be inclined along the support portion, the object to be charged is held inclined to thereby widen a battery charging distance, thereby effecting a low-rate charge, whereas when vertically placed, the object to be charged and the battery charger get close to each other to narrow the battery charging distance, thereby effecting a quick charge. This charging system, however, is not suitable for in-vehicle use, as it is difficult to charge the object with the object being vertically placed in a moving vehicle.
Further, as another charging system for simplifying an efficient charge, there has been proposed an inductive charging pad with a placement indicator, as disclosed in e.g., Japanese unexamined patent application publication No. 2006-94699. In the publication No. 2006-94699, it is proposed that a graphic representation of an electric device is disposed on a charging surface of a battery charger to indicate a position of a primary coil disposed within a boundary of the graphic representation. When the electric device is placed on the graphic representation, the electric device is aligned with the graphic representation, and thus the primary coil of the battery charger becomes aligned with a secondary coil of the electric device, whereby positioning the electric device within the boundary of the graphic representation facilitates efficient inductive power transfer. According to this technique, however, if the electric device itself is changed or replaced with that of another type, the graphic representation also needs to be changed accordingly, thus leading to inconvenience.
On the other hand, there has been proposed yet another contactless battery charging system, as disclosed in e.g., Japanese unexamined patent application publication No. 2008-301554. According to this battery charging system, communication with a device to be charged placed on a placing portion enables information on the device to be charged to be imported, and then based on the information thus imported, a placing position (an outer frame) of the device to be charged and a position of a primary transmission coil are displayed on a liquid crystal display section provided on the placing portion to thereby guide the device to be charged to a precise position on the placing portion, thus enabling the device to be charged to be easily placed thereon. According to this contactless charging system, information about placing position specific to respective specific devices to be charged is retrieved from a database so that a display means is controlled in such a way that the placing position of the device to be charged is displayed based on the placing position information thus retrieved. In this manner, this contactless charging system can be adapted to a plurality of devices, yet there remains a problem that it cannot be used for devices not registered in the database.